How many points can a cannon reach from the center of the board?
These answers restate the rules implemented by our open-source engine, which follows the WXF laws and is regression-tested against the official 110-diagram repetition casebook. Where an answer refers to a specific position, that position lives on the linked reference page, where the build verifies it against the engine before publishing.
Direct answer
On an otherwise empty board, a cannon standing on a central point can reach up to seventeen points: all eight remaining points along its rank, since the board is nine files wide, and all nine remaining points along its file, since the board is ten ranks tall. In a real game, other pieces reduce that sharply and also create the screens it needs to capture.
Why the raw number overstates its opening strength
Seventeen points of pure movement sounds like a lot, but early in the game most of that reach is blocked by other pieces, and blocked lines are exactly what a cannon needs anyway, since it captures by jumping a single piece rather than sliding freely. Its true threat range depends entirely on where screens happen to sit.
How this compares to a chariot
A chariot on the same central point has the identical seventeen-point reach on an empty board, but every one of those points is a genuine attacking threat if occupied by an enemy piece, since a chariot simply captures whatever it reaches. The cannon's reach and its threat range are two different things; the chariot's are the same thing.
Related questions
Does a cannon in a corner reach fewer points?
Yes, corner and edge points reduce both the rank and file lengths available, the same as for a chariot.
Is seventeen points the most any piece can reach?
It ties the chariot for the most of any piece on an empty board; no other xiangqi piece reaches that many points from one square.
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